Summary:
YnfE has been implicated as a Tat-dependent selenate reductase enzyme in E. coli. A ynfEF double null mutant is unable to reduce selenate to elemental selenium [Guymer09]. The disruption is specific to the initial selenate reduction process since selenium production is restored when selenite is added to the growth medium [Guymer09]. Production of either YnfE or YnfF from a plasmid restored the ability of the E. coli ynfEF double mutant to reduce selenate to selenium in vivo [Guymer09].

YnfE is highly similar to DmsA, the catalytic subunit of the dimethyl sulfoxide reductase heterotrimer, and cross-reacts with an anti-DmsA antibody. The protein is poorly expressed. In a plasmid expression system, expression of YnfE appears to inhibit expression of YnfFGH [Lubitz03].

In a ΔtusA strain, expression of ynfE is decreased in mid-exponential phase and under aerobic conditions [Dahl13].

Summary:
On the basis of sequence similarity the ynfEFGH operon was predicted to encode an oxidoreductase complex closely related to DMSO reductase. A strain carrying a deletion of dmsABC and containing ynfFGH on a multicopy plasmid is able to grow poorly under anaerobic conditions utilizing dimethyl sulfoxide as a terminal oxidant [Lubitz03]. More recently, genetic analysis of E.coli ynfE and ynfF null mutants suggests these proteins are Tat-targeted selenate reductases [Guymer09]. E.coli ubiE and menA null mutants are unable to reduce selenate to elemental red selenium in vivo thus implicating menaquinone in the reductase activity [Guymer09].